Fabrication of integrated circuitry (IC) often involves formation of photolithographically-patterned photoresist over a semiconductor substrate. The patterned photoresist may then be utilized as a mask during subsequent patterning of the underlying substrate, and/or during implant of dopant into the underlying substrate. Alternatively, sidewall spacers may be formed along edges of the patterned photoresist, and the photoresist may then be removed to leave the sidewall spacers as a mask which may be utilized during subsequent patterning of the underlying substrate and/or during implant of dopant into the underlying substrate. An advantage of utilizing the sidewall spacers as the mask is that the sidewall spacers may be formed at a pitch which is about half the starting pitch of the patterned photoresist.
In many applications, it is desired that photolithographically-patterned photoresist form features having vertical sidewall edges. A difficulty that may be encountered during utilization of photolithographically-patterned photoresist is that the photoresist features may have sidewall edges that are not as vertical as desired.
FIG. 1 shows a prior art semiconductor construction 10 having photolithographically-patterned photoresist 14 over a semiconductor substrate 12.
Substrate 12 may comprise, consist essentially of, or consist of, for example, monocrystalline silicon lightly-doped with background p-type dopant. The terms “semiconductive substrate” and “semiconductor substrate” mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” means any supporting structure, including, but not limited to, the semiconductive substrates described above.
Photoresist 14 is patterned into three features 16, 18 and 20, with such features being spaced apart from one another by intervening gaps 22 and 24. The features 16 and 18 are about the same width as one another, while the feature 20 is much wider than features 16 and 18.
Feature 16 has sidewall edges 11 and 13, feature 18 has sidewall edges 15 and 17, and feature 20 has a sidewall edge 19. The sidewall edges 11, 13, 15 and 17 are substantially vertical, while the sidewall edge 19 is not vertical.
Referring to FIG. 2, a layer 26 is formed over features 16, 18 and 20, as well as within the gaps between such features.
Referring to FIG. 3, layer 26 is subjected to an anisotropic etch which converts the layer into a plurality of structures 28, 30, 32, 34 and 36. The structures 28, 30, 32 and 34 are substantially the same as one another in configuration, but the structure 36 is different than features 28, 30, 32 and 34 due to edge 19 being non-vertical.
Referring to FIG. 4, photoresist 14 (FIG. 3) is removed to leave structures 28, 30, 32, 34 and 36 over substrate 12. Ideally, structures 28, 30, 32, 34 and 36 would be a repeating pattern of substantially identical structures corresponding to the desired pattern shown in FIG. 5. However, structure 36 of FIG. 4 does not have the appropriate shape to fall within the desired repeating pattern. This can detrimentally affect subsequent processing. For instance, if structures 28, 30, 32, 34 and 36 are to be used for patterning underlying substrate 12 into a plurality of substantially identical repeating elements, the inconsistent shape of structure 36 relative to the other structures may lead to formation of an element which is defective for its intended purpose.
It would be desirable to develop improved methods for formation of photolithographically-patterned photoresist which alleviate, or prevent, the prior art problems discussed above with reference to FIGS. 1-4.